I drink diet pop. Though on its face that doesn’t seem controversial, I find myself regularly defending my beverage choice when I crack open a can of Diet Coke. People say it’s bad for me, or it’s “unhealthy”. Why do they think that? My guess is that many people believe that since diet pop contains “artificial” ingredients, it’s not “natural”1, and therefore it’s not “healthy” to drink. When I ask which ingredients in diet pop are “unhealthy”, many people target aspartame. Though I’m not motivated to argue why aspartame might be healthy (or not unhealthy), I’ve thought about the chemical’s safety enough to want write about it here2.

Aspartame is safe

The Food and Drug Administration (FDA) claims, “Aspartame is one of the most exhaustively studied substances in the human food supply, with more than 100 studies supporting its safety.” This claim concerns the general population, but, “people with a rare hereditary disease known as phenylketonuria (PKU) have a difficult time metabolizing phenylalanine, a component of aspartame, and should control their intake of phenylalanine from all sources, including aspartame.” Depending on the country, PKU affects between 1 in 10,000 and 1 in 20,000 individuals, according to the National PKU Alliance.

Patients at our diabetes clinic have raised concerns about information on the internet about a link between the artificial sweetener aspartame and various diseases. Our research revealed over 6000 web sites that mention aspartame, with many hundreds alleging aspartame to be the cause of multiple sclerosis, lupus erythematosis, Gulf War Syndrome, chronic fatigue syndrome, brain tumours, and diabetes mellitus, among many others. Virtually all of the information offered is anecdotal, from anonymous sources and is scientifically implausible.

I think it’s safe to say the number of websites has increased since then. When I Google “aspartame health”, the search returns, “About 1,300,000 results.” Moreover, check out the Google Trend graph below for “aspartame effects” searches since 2004:

According to Google, numbers represent search interest relative to the highest point on the chart. If at most 10% of searches for the given region and time frame were for “pizza,” we’d consider this 100. This doesn’t convey absolute search volume.

These men go onto to explain:

Aspartame, a dipeptide composed of phenylalanine and aspartic acid linked by a methyl ester bond, is not absorbed, and is completely hydrolysed in the intestine to yield the two constituent amino acids and free methanol. Opponents of aspartame suggest that the phenylalanine and methanol so released are dangerous. In particular, they assert that methanol can be converted to formaldehyde and then to formic acid, and thus cause metabolic acidosis and neurotoxicity.

Although a 330 mL can of aspartame-sweetened soft drink will yield about 20 mg methanol, an equivalent volume of fruit juice produces 40 mg methanol, and an alcoholic beverage about 60–100 mg. The yield of phenylalanine is about 100 mg for a can of diet soft drink, compared with 300 mg for an egg, 500 mg for a glass of milk, and 900 mg for a large hamburger1(my emphasis). Thus, the amount of phenylalanine or methanol ingested from consumption of aspartame is trivial, compared with other dietary sources. Clinical studies have shown no evidence of toxic effects and no increase in plasma concentrations of methanol, formic acid, or phenylalanine with daily consumption of 50 mg/kg aspartame (equivalent to 17 cans of diet soft drink daily for a 70 kg adult)1,2.

ADA position statement: use of noncaloric sweeteners. Diabetes Care. 1991

But to be clear, extremely high does of aspartame may have negative health effects. The FDA has set aspartame’s Acceptable Daily Intake (ADI) to 50 milligrams per kilogram of body weight per day, or the equivalent of a 60-kilogram (132-pound) individual consuming 75 tabletop sweetener packets or 24 cans of Diet Coke.

To make the graph, I used 35mg of aspartame in 1 packet of Equal and the 5th percentile weight of an 18 year old female in the U.S. = 65 kg (143 lb.) as a starting point. The latter represents arguably the lightest adult weight percentile in the U.S.125 mg of aspartame in 12-oz Diet Coke

Don’t trust the FDA or some concerned doctors from 15+ years ago? Fair enough. In 2007, Magnuson et al. published a review of the scientific literature on, “the absorption and metabolism, the current consumption levels worldwide, the toxicology, and recent epidemiological studies on aspartame.” They came to conclusions similar to the FDA:

Current use levels of aspartame, even by high users in special subgroups, remains well below the U.S. Food and Drug Administration and European Food Safety Authority established acceptable daily intake levels of 50 and 40 mg/kg bw/day, respectively

Acute, subacute and chronic toxicity studies with aspartame, and its decomposition products, conducted in mice, rats, hamsters and dogs have consistently found no adverse effect of aspartame with doses up to at least 4000 mg/kg bw/day.

No credible evidence that aspartame is carcinogenic.

No support that aspartame in the human diet will affect nervous system function, learning or behavior.

Very recently (2015), Mallikarjuna & Sieburth conducted a meta-analysis (read: study of studies) of 10 aspartame carcinogenic bioassays on rodents (read: they measured cancer in rodents exposed to aspartame). Similar to above, they found (wait for it):

Based on the current body of scientific evidence, aggregate effect sizes revealed that APM [aspartame] consumed at any dose level has no significant relationship with cancer (occurrence of malignant tumors).

In sum, the weight of the evidence from my casual search suggests that consuming even reasonably large amounts of aspartame is safe for the general population.

That’s aspartame, but what about the other ingredients in diet soda?

Though I think it’s unlikely that aspartame consumption poses any serious saftey threats, diet soda contains other ingredients that may. For instance, many soft drinks, diet soda included, contain caramel color, which is made with ammonium compounds whose manufacture can result in the formation of 4-methylimidazole (4-MEI). 4-MEI is linked to cancer in mice and listed as a carcinogen under the Safe Drinking Water and Toxic Enforcement Act of 1986. In short, caramel color in many sodas maycausecancer. Coke changed its caramel color and Pepsi claims to be doing the same.

Ingredients aside, pop in general is acidic, so it’s probably bad for your teeth. Does that make is unsafe? If you want to claim that eroding enamel has long-term negative health effects, so then drinking diet pop in unsafe, go ahead. Then so is drinking any pop, and yet no one scoffs when someone opens a regular Coke (not because of cancer or toxicity at least).

So…?

It seems to me that diet pop is a low-risk beverage choice. I’m going to keep drinking it and rolling my eyes when people tell me I’m going to get cancer.

What’s the difference between natural and artificial? There are likely few if any food stuffs in a grocery store that haven’t been adjusted by farmers or scientists or both to meet the preferences and saftey of consumers. Though we can all get a feel for what these words mean when people use them, they’re super hard to really define and I’m just not going to here.

Healthy is obvious in some senses (e.g., not having Ebola) and less so in others (e.g., time it takes someone to run a mile). I think it’s easier to talk about the safety rather than the healthiness of a chemical, so I’m doing that.

I used a list I found here to make my list of mythical links to aspartame

Imagine an NBA player has an 80% chance to make one free throw. What is the chance that he makes both free throws? The correct answer is 64% (80% * 80%).

Now consider the possibility that it is possible to distinguish between two types of free throws. Some free throws are good; they don’t touch the rim and make a swishing sound when they go through the net (all net). The other free throws bounce of the rim and go in (rattling in).

What is the probability that an NBA player with an 80% free throw percentage makes a free throw that is all net or rattles in? It is more likely that an NBA player with an 80% free throw average makes a perfect free throw because a free throw that rattles in could easily have bounded the wrong way, which would lower the free throw percentage. To achieve…

Life is a succession of tasks rather than a cascade of inspiration, an experience that is more repetitive than revelatory, at least on a day-to-day basis. The thing is to perform the task well and find reward even in the mundane.

This is not a world where you can simply express love for other people, where you can praise them. Perhaps it should be. But it’s not. I’ve found that people will fear your enthusiasm and warmth, and wait to hear the price. Which is fair. We’ve all been drawn into someone’s love only to find out that we couldn’t afford it. A little distance buys everyone time.

In 1972, Cecil Clayton, then 31, was sawing a log in a lumberyard when a wood splinter ricocheted from his blade and struck his left temple. He recovered after nine days in the hospital, but he lost about 20% of his prefrontal lobe. After his recovery, according to his brother, Cecil, “broke up with his wife, began drinking alcohol and became impatient, unable to work and more prone to violent outbursts.” Then, twenty-four years later in 1996, Clayton shot and killed sheriff deputy Christopher Casetter.

If you’ve ever taken an introductory psychology class, Clayton’s accident and subsequent pattern of behavior might seem familiar to you. You may remember that in 1848, the young railroad company foreman Phineas Gage suffered a similar injury. He was drilling a hole in some rock and he used an iron rod to pack the hole with gunpowder, which then exploded, sending the rod through his cheekbone and out the top of his head. Gage got up from his injury still walking and talking, but, legend has it, he soon became a temperamental and violent drunk.

Computer generated depiction of where the iron rod penetrated and left Phineas Gage’s skull.

However, people close to Gage report he still warmly entertained his nieces and became fond of animals; others report he was physically and mentally fit enough to drive a 60-mile stage couch in another country. Though, “he was no longer Gage,” following his accident, whether he became unstable and violent isn’t factual.

Clayton’s behavior, however, is better documented and has more clearly taken a turn for the worse. For example, he scored a 71 (± 4 to 5 points) on his most recent IQ test*. Moreover, since his accident,

He has the reading ability of a nine-year-old, has visual and auditory hallucinations in which he is convinced that he is accompanied by a man and a woman wherever he goes, is incapable of simple tasks such as ordering food from the prison commissary, and is under the delusion that he will never be executed because God will intervene and free him so that he can return to his preaching and gospel singing.

Ed Pilkington, The Guardian

Clayton, 74, is surely mentally disabled, yet the same year he killed Casetter, he was sentenced to death in Missouri. Recently, on Saturday, March 14th, he was denied a mental competency hearing, the only chance for him to establish his disability and save his life. Yet even if his lawyers were succesful in attaining such a hearing, it may not nullify his death sentence. Though the Supreme Court has repeatedly ruled that the 8th amendment excludes the execution of the “intellectualy disabled”, each state is allowed to use its own definition of intellectually disabled. Clayton’s fate may very well boil down to Missouri’s statute that requires intellectual disability be established by the time the inmate turns 18. That is, it wouldn’t matter if Clayton had lost half his brain and most mental capacities imaginable by age 19; his tragic mental state would be irrelevant to his execution ruling. So, barring intervention by the U.S. Supreme Court or the governor of Missouri, Clayton will die today by lethal injection.

Cecil Clayton is reasonably a dangerous man. However, given the state of his mind, it’s cruel to execute him. One psychologist noted Clayton, “is not simply incompetent legally, he would be unable to care for himself or manage basic self-care, were he not in a structured environment that takes care of him … he still does not comprehend, appreciate nor understand its approaching date for him.” What purpose would be served by killing this person?

Maybe retribution? I might suffer from a lack of imagination, but I can’t fathom retributive justice—essentially state condoned vengenece—as ever being good reason for any punishment, let alone execution. Perhaps, though, executing Clayton will serve some sort of deterrent purpose? This I think is even more ridiculous than retributive justice: executing Clayton to set an example for the rest of the mentally disabled also contemplating murder. In other words, the hope would be that other mentally disabled men and women would, upon learning the news of Clayton and others’ fates, consider the serious legal consequences of murder.

No.

So whether it’s to exact vengeance or deter future mentally handicapped murderers, I have difficulty not guffawing at the thought of any reason to execute Clayton or anyone like him. Moreover, the absurdity of furnishing any good reason to execute a man with a hole in his brain should call into question the very idea of executing anyone. Indeed, former Supreme Court Justice Harry Blackmun, who in 1976 voted to reinstate the death penalty in Gregg v. Georgia, famously renounced his position on the death penalty, stating, “From this day forward, I no longer shall tinker with the machinery of death.” Yet, on we tinker.

The initial organization of the brain does not depend that much on experience.Nature provides a first draft, which experience then revises.Built-in doesn’t mean unmalleable;it means organized in advance of experience.